.box {
  background-color: #ddd;
  .back {
    display: none;
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 48px;
    background-color: rgba(0, 0, 0, 0.5);
    padding: 5px 8px;
    border-radius: 3px;
    color: #ffffff;
    cursor: pointer;
    &:hover {
      background-color: rgba(0, 0, 0, 0.7);
    }
  }
}
